Conventionally, in an electric car or a hybrid car, as shown in FIG. 6 related to a hybrid car described in JP 2010-36594A, a high-voltage battery pack 100 is disposed on a rear side in a vehicle compartment, or the like, and the battery pack is connected to an apparatus 103 mounted in an engine room via a high-voltage power cable 101. In the apparatus 103, the battery pack is connected to a fuse 104 and a DC/DC module 105 that is disposed integrally with or in proximity to a high/low-voltage junction box.
When a relay is mounted on the junction box, generally, as shown in FIG. 7, a relay 201, which is a heat generating element, is often mounted on the upper side of an upper case 202 of a junction box 200 to suppress overheating inside the junction box 200. When the relay 201, which has a high profile, is mounted on the upper side of the junction box 200, the height H2 of the relay 201 is added to the height H1 of the junction box 200 and the total height is increased.